Exposure apparatus and exposure method thereof

ABSTRACT

An exposure apparatus is provided for performing an unidirectional scan-exposure. The exposure apparatus includes a base and a wafer stage group having a plurality of wafer stages on the base for holding wafers and successively moving from a first position to a second position of the base cyclically. The exposure apparatus also includes an alignment detection unit above the first position for detecting wafer stage fiducials at the first position and alignment marks on a wafer on the wafer stage to align the wafer. Further, the exposure apparatus includes a reticle stage on the second position for loading a cylindrical reticle and causing the cylindrical reticle to rotate around the center axis of the reticle stage and an optical projection unit between the reticle stage and the base for projecting light passing through the cylindrical reticle onto exposure regions on a wafer on the wafer stage.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of Chinese patent application No.201310069610.2, filed on Mar. 5, 2013, the entirety of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to the field of semiconductormanufacturing technology and, more particularly, relates to exposureapparatuses and exposure methods thereof.

BACKGROUND

Photolithography process is a very important process of thesemiconductor manufacturing technology, which transfers patterns on amask to a substrate by an exposure process. The photolithography processis a core step of the manufacturing of large scale integrations (LSIs).The complex and time-consuming photolithography process of thesemiconductor manufacturing technology is mainly performed bycorresponding exposure apparatus. Further, the development of thephotolithography technology or the improvement of the exposure apparatusare mainly focused on three specifications including feature size,overlay resolution, and yield.

In the manufacturing of a semiconductor device, the photolithographyprocess may include three main steps: changing wafers on the waferstages; aligning the wafers on the wafer stages; and transferringpatterns on the mask to the wafers. These three steps may besequentially repeated on the same wafer stage.

Since the photolithography process is a key step of the semiconductormanufacturing process, how to improve the yield of an exposure apparatusin the practical manufacturing process have become a very importanttopic. Various exposure apparatuses with twin-stages have been developedin past a few years in order to further increase the yield of theexposure apparatuses.

FIG. 1 illustrates an existing exposure apparatus with twin-stages. Theexposure apparatus includes a first stage 101 and a second stage 102 forholding wafers; an alignment detection unit 103 for detecting alignmarks on wafers and aligning wafers; a mask stage 107 for holding a mask108; an optical projection unit 104 under the mask stage 107 forprojecting light through the mask 108 on the wafers on the first stage101 or the second stage 102 and performing an exposure on the wafers;and an illuminator 109 above the mask stage 107 for providing anexposure light.

An exposure process using the existing tool may include sequentially:aligning the first wafer 106; moving the first stage 101 under theoptical projection unit 104; and performing an exposure on the firstwafer 106 using the optical projection unit 104 which projects lightthrough the mask 108 on the first wafer 106. At the same time, a secondwafer 105 may be installed on the second stage 102, and moved under thealignment detection unit 103. The alignment detection unit 103 maydetect the alignment mark on the second wafer 105 on the second stage;and the second wafer 105 may be aligned. After the first wafer 106 isexposed, a new wafer may be installed on the first stage 101, and thefirst stage 101 with the new wafer may be moved under the alignmentdetection unit 103. The alignment detection unit 103 may align the newwafer. At the same time, the second stage 102 may be moved under theoptical projection unit 104, and the second wafer 105 may be exposed bythe optical projection unit 104.

However, even with such improvements, the exposure efficiency and theyield of the existing exposure apparatuses may still be relatively low.The disclosed methods and systems are directed to solve one or moreproblems set forth above and other problems.

BRIEF SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure includes an exposure apparatus forperforming an unidirectional scan-exposure. The exposure apparatusincludes a base and a wafer stage group having a plurality of waferstages on the base for holding wafers and successively moving from afirst position to a second position of the base cyclically. The exposureapparatus also includes an alignment detection unit above the firstposition for detecting wafer stage fiducials at the first position andalignment marks on a wafer on the wafer stage to align the wafer.Further, the exposure apparatus includes a reticle stage on the secondposition for loading a cylindrical reticle and causing the cylindricalreticle to rotate around the center axis of the reticle stage and anoptical projection unit between the reticle stage and the base forprojecting light passing through the cylindrical reticle onto exposureregions on a wafer on the wafer stage.

Another aspect of the present disclosure includes an exposure method.The exposure method includes a Step 1 for installing wafers successivelyon a plurality of wafer stages and a Step 2 for moving the wafer stagesholding wafers to a first position successively, detecting stagefiducials on the wafer stages and alignment marks on the wafers to alignthe wafers. The exposure method also includes a Step 3 for moving thewafer stage having the aligned wafer from the first position to a secondposition and performing an unidirectional scanning along a scandirection; rotating a cylindrical reticle around the center axis of areticle stage; projecting light passing through the cylindrical reticleonto the wafer on the wafer stage; and exposing a first column ofexposure regions along the scanning direction. Further, the exposuremethod includes a Step 4 for moving the wafer stage holding thepartially exposed wafer from the second position to the first positionafter exposing the first column of exposure regions and a Step 5 forrepeating the Step 2 to the Step 4 until a predetermined number ofcolumns of exposure regions of the wafer on the wafer stage are exposed

Other aspects of the present disclosure can be understood by thoseskilled in the art in light of the description, the claims, and thedrawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an existing exposure apparatus and exposure process;

FIG. 2 illustrates scanning directions for each exposure regions of theexisting exposure apparatus;

FIGS. 3-6 illustrate certain structures of an exemplary wafer stageconsistent with the disclosed embodiments; and

FIGS. 7-14 illustrate certain steps of an exemplary wafer scanningprocess consistent with the disclosed embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of theinvention, which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

FIG. 2 illustrates scanning directions of the existing exposureapparatus for each exposure regions of a wafer, i.e., the direction ofan arrow may refer to the scanning direction. For example, referring toFIG. 1, for each scanning, the stage (the first stage 101 or the secondstage 102) may move along the scanning direction, and the mask stage 107with the mask 108 may move along an opposite direction, and a firstexposure region may be exposed. After exposing the first exposureregion, a second exposure region may be exposed.

As shown in FIG. 2, the first wafer 106 may have a plurality of exposureregions. Referring FIGS. 1-2, the first stage 101 may move along a firstdirection to scan and expose a first exposure region 11. Wherein thefirst direction is the direction of the arrow shown in first exposedregion 11. After exposing the first exposure region 11, a secondexposure region 12 adjacent to the first exposure region 11 may beexposed by moving the first stage 101 with a direction opposite to thefirst direction which may be referred as a second direction as shown inthe second exposure region 12. Scanning (or exposures) along the firstdirection and the second direction may be sequentially repeated untilall the exposure regions of the first wafer 106 are exposed.

An accelerating process, a scanning and exposing process and adecelerating process may thus exist in every scanning (or exposure) whenthe existing exposure apparatus (or method) is used. The acceleratingprocess and the decelerating process may be used to improve the accuracyand efficiency of changing exposure regions, they may be unable to aidthe actual exposure of wafers although occupying a portion of the totaltime of the exposure process. Thus, the accelerating process and thedecelerating process may waste time, and may cause a relatively lowyield in per unit time.

FIGS. 3-6 illustrate certain structures of an exemplary exposureapparatus consistent with the disclosed embodiments.

FIG. 3 illustrates an exemplary exposure apparatus. As shown in FIG. 3,the exposure apparatus includes a base (not shown). The base may providea moving region for wafer stages. The base may be designed with anyappropriate size and geometry. Certain damping system may also beincluded in the base to reduce vibration, or other kind of noises. Othernecessary components may also be installed in the base to make it havedesired functionalities.

The exposure apparatus also includes a stage group on the base which isused to hold, load and unload wafers. The stage group may have aplurality of wafer stages 301. The plurality of wafer stages 301 maysequentially circularly move between a first position (pre-alignposition) and a second position (pre-exposure position). The stage groupmay be controlled by a close-loop control system, or an open-loopcontrol system, etc.

Further, the exposure apparatus includes an alignment detection unit 302above the first position 311 of the base. The alignment detection unit302 may be used to detect stage fiducials on the wafer stages 301 at thefirst position. The alignment detection unit 302 may also be used todetect alignment marks on wafers on the wafer stages 301, and align thewafers. Various sensors may be used in the alignment detection unit 302,such as a laser sensor, an infrared sensor, or an position sensor, etc.

Further, the exposure apparatus also includes a cylindrical reticlestage 305 above the second position of the base. The cylindrical reticlestage 305 may be used to hold a cylindrical reticle 303 through a firstbearing 304 a and a second bearing 304 b, and to cause the cylindricalreticle 303 to rotate along the center axis of the cylindrical reticlestage 305.

Further, the exposure system also includes an optical projection unit309 between the cylindrical reticle stage 305 and the base. The opticalprojection unit 309 may project light onto exposure regions of thewafers on the wafer stages 301, and perform exposure. After the waferstages 301 move from the first position 311 to the second position 312,an unidirectional scan may be performed along a scanning direction. Thecylindrical reticle 303 may rotate along the center axis of thecylindrical reticle stage 305, the light through the cylindrical reticle303 may be projected on the wafer on the wafer stage 301. Thus, a columnof exposure regions on the wafer along the scanning direction may beexposed.

Further, the exposure apparatus may also include a main control unit300. The main control unit 300 may communicate with the wafer stages301, the alignment detection unit 302, the cylindrical reticle system305, and the optical projection unit 309, etc. The main control unit 300may be used to manage wafer alignment and exposure processes. The maincontrol unit 300 may also be used to send out various kinds of commands,receive feedback information from various units, manage positioninformation, and calculate lateral movement constants, rotationconstants, and amplification constants of the wafer stages 301 and thecylindrical reticle 303.

Further, the exposure apparatus may also include an encoder plate 306having a first opening 311 and a second opening 312. The encoder plate306 may be used to align wafers, wafer stages 301 and cylindricalreticle 303, etc.

Further, the exposure apparatus may also include a plurality of cablesand connectors, such as charging cables 307 and charging ports 308 forcharging a power source of the wafer stages 302. Other cables may alsobe used for communications of different components.

Further, the exposure apparatus may also include an illuminator box 308.The illuminator box 308 may have a light source inside. The light sourcemay be used to expose the wafers.

Further, the exposure apparatus may also include a time fiducial unit(not shown). The time fiducial unit may be used to provide a fiducialtime unit signal, and cause the collection of all signals of the waferalignment and exposure processes to be related with time.

The detailed structures of the exposure apparatus are described belowtogether with various illustrative drawings.

Referring to FIG. 3, the wafer stages 301 may be driven by a magneticsuspension system to move along a scanning direction (the arrowdirection) in the xy-plane. The wafer stages 301 may also move from afirst position to a second position by the magnetic suspension system.The wafer stages 301 may move along the positive direction of the y-axis(the scanning direction), the negative direction of the y-axis, thepositive direction of the x-axis, the negative direction of the x-axis,the positive direction of the z-axis, and the negative direction of thez-axis.

The magnetic suspension system may be a maglev planar motor. The statorof the maglev planar motor may be fixed on the top surface of the base.The rotor of the maglev planar motor may be fixed on the bottom surfaceof the wafer stages 301. The maglev planar motor may be a permanentmagnet dynamic maglev planar motor, a permanent magnet moving-ironmaglev planar motor, or a maglev induction planar motor, etc.

The wafer stages 301 may sequentially move on the base. As shown in FIG.3, when a plurality of wafer stages 301 carrying wafers are sequentiallyaligned at the first position, they may sequentially move to the secondposition. At the same time, the cylindrical reticle 303 may rotatearound the center axis of the cylindrical reticle stage 305. The lightpenetrating through the cylindrical reticle 303 may be projected on thewafer on one wafer stage 301, thus a column of exposure regions alongthe scanning direction may be exposed. After exposing the column of theexposure regions, the wafer stage 301 may sequentially move from thesecond position to the first position to perform an alignment. Thealignment and exposure processes may be repeated until the entire waferare exposed.

When the wafer is exposed, it may unnecessarily need to change thescanning direction the wafer stages 301. At the same time, it mayunnecessarily need to change the rotation direction of the cylindricalreticle 303 as well. Thus, it may unnecessarily need to have adeceleration and an acceleration process during the process for exposingeach exposure area, a total exposure time of each exposure region may besignificantly reduced. The yield in per unit time of the exposureapparatus may be significantly increased.

The wafer stages 301 may have corresponding sub control units (notshown). The sub control units may be inside of the wafer stages 301. Thesub control units may be used to control the position of the waferstages 301, the movement of the wafer stages 301, and the alignment ofthe wafers. The sub control units may communicate with the main controlunit 300, the magnetic suspension system, the alignment detection unit302, and the cylindrical reticle stage 305.

In one embodiment, when performing an exposure process, the wafer stages301 may scan along one direction of the y-axis with a pipeline mode. Thecylindrical reticle 303 may rotate around the center axis of thecylindrical reticle system 305, the light passing through thecylindrical reticle 303 may be projected on the wafer on the waferstages 301, thus a column of exposure areas on the wafer may be exposed.

Therefore, a number of the wafer stages 301 may be greater than, orequal to two, which may increase the number of wafers carried by thewafer stages 301, and improve the efficiency of the exposure. In oneembodiment, the number of the wafer stages 301 may be 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25,etc.

If the number of the wafer stages 301 is two, the sub control units onthe wafer stages 301 may communicate with the main control unit 300, thealignment detection unit 302 and the cylindrical reticle stage 305,etc., with a wired connection. In certain other embodiments, when thenumber of the wafer stages 301 is two, the sub control units on thewafer stages 301 may communicate with the main control unit 300, thealignment detection unit 302 and the cylindrical reticle stage 305 etc.,with a wireless communication method.

In certain other embodiments, when the number of the wafer stages 301 isgreater than two, the sub control units on the wafer stages 301 maycommunicate with the main control unit 300, the alignment detection unit302 and the cylindrical reticle system, etc., with a wirelesscommunication method. Since the wafer stages 301 may move circularly onthe base, the wireless communication method may avoid the difficultiesof placing wires and the movement of the wafer stages 301 which may berequired for the wired communication method.

The wireless communication method may include a bluetooth technology, ainfrared data association technology, a wireless fidelity (Wi-Fi)technology, a wireless application protocol (WAP), an ultra widebandtechnology, or a near field communication (NFC) technology, etc.

In one embodiment, if a wireless communication technology is used forthe wafer stages 301 to communicate with peripheral circuits, each ofthe wafer stage may have a power storage unit (not shown) used to storethe power for operating the wafer stages 301. The power for operatingthe wafer stages 301 may include the power for moving the wafer stages301, the power for operating the sub control units, and the power forthe communication between the wafer stages 301 and the peripheralcircuits. The power storage unit may be fast charging battery packs, orsuper capacitors, which may be able to store a relatively large amountof power, and may be charged in a relative fast speed.

As shown in FIG. 3, in order to charge the power storage unit of thewafer stage 301, the exposure apparatus may have the charging cable 307and the charging port 310. When the charging cable 307 is connected withthe charging port 307, the charging cable may charge the power storageunit of the wafer stage 301.

If the number of the wafer stages 301 is 2, the charging cable 307 andthe charging port 310 may be connected with an immovable method.

If the number of the wafer stages 301 is equal to, or greater than two,the exposure apparatus may have a cable connection unit (not shown). Thecable connection unit may be used to form a detachable connectionbetween the charging cable 307 and the power storage unit on the waferstages 301. When the wafer stages 301 move to a certain position (suchas the first position), a connection may be formed between the chargingcable 307 and the charging port 310 by the cable connection unit, thecharging cable 307 may charge the power storage unit.

When the charging cable 307 moves to a next position (such as the secondposition) with the wafer stages 301, the charging cable 307 maydisconnect with the charging port 310 by the cable connection unit, acharging process may be finished. When a plurality of wafer stages 301moves cyclically, the difficulties for arranging wires may beeffectively solved. The charging process may be performed during anexposure process.

In certain other embodiments, the charging process may be performed whenthe exposure apparatus is at a standby status. Specifically, when thewafer stages 301 are moving to a certain position, a connection may beformed between the charging cable 307 and the power storage unit on thewafer stage 301 by the cable connection unit, the power storage unit maybe charged by the charging cable 307, and the wafer stages 301 and thecharging cable 307 may be kept static. After a certain period of time,the charging cable 307 may disconnect with the wafer stage 301 by thecable connection unit.

The cable connection unit may include a clamping unit (not shown) and adrive unit (not shown). The clamping unit may be used to clamp thecharging cable 307, and move the charging cable 307 in a micrometerscale. The drive unit may be used to cause the clamping unit to movealong the x-axis, the y-axis and the z-axis, and to rotate around thex-axis, the y-axis and the z-axis.

In order to achieve an accuracy position of multiple wafer stages 301,the exposure apparatus may have position detection units. Referring toFIG. 3 and FIG. 4, the position detection unit may include the alignmentdetection system 302, the encoder plate 306 between the opticalprojection unit 309 and the wafer staged 301, and encoder plate readers313 on the top surface of the wafer stages 301.

As shown in FIG. 4, the top surface of the wafer stage 301 may have awafer loading region 314 and a peripheral region 315 surrounding thewafer loading region 314. The encoder plate readers 313 may be at theperipheral region 315 of the top surface of the wafer stage 301. Each ofthe encoder plate readers 315 may have two encoder detector units 318.Each of the encoder detector units 318 may have optical emission units(not shown), optical receiver units (not shown), and sub recognitionunits (not shown), etc.

The optical emission units may be used to emit a detection light. Theoptical receiver units may be used to receive the light reflected by theencoder plate 306, and covert the light signal to an electric signalvarying with time. The sub recognition units may be used to perform asignal amplification process, a signal filtering process, a directionsensing process, a pulse width calculation process, and/or a datacounting process, etc, thus the displacement of the wafer stage 310 maybe found after a signal processing.

When a number of the encoder plate readers 315 is greater than one, eachof the sub recognition units may send signals processed by amplifying orfiltering, etc., to a main recognition unit (not shown). The mainrecognition unit may perform a direction sensing process, a pulse widthcalculation process, and/or a data counting process, etc., thus thedisplacement of the wafer stage 301 may be found. A direction of thelight emitted from the optical emission unit may be inclined to theencoder plate 306, that is, the irradiating direction of the emissionlight may have a certain angle with the normal of the encoder plate 306,which may cause the reflected optical signal from the encoder plate 306to have a relatively large amplitude. Further, the emission light on thetwo encoder detector units 318 may be both inclined to a directionopposite to the two encoder detector units 318, which may cause the twoencoder detector units 318 to have different phases when the wafer stage301 moves along the z-axis. Thus, the displacement of the wafer stage301 along the z-axis direction may be determined.

The number of the encoder plate readers 313 may be at least three. Thethree encoder plate readers 313 may be distributed at differentpositions of the peripheral region 315 of the wafer stage 301. In oneembodiment, the number of the encoder plate readers 313 is four. Thefour encoder plate readers 313 are at the four corners of the peripheralregion 315 of the wafer stage 301. A distance between each of theencoder plate readers 313 and the center of the wafer stage 301 may beequal or different.

Referring to FIG. 4, each of the encoder plate readers 313 may have azeroing mark detection unit 317. The zeroing mark detection unit 317 maybe used to detect a zeroing mark on the encoder plate 306. In oneembodiment, the zeroing mark detection unit 317 may be an imagingalignment sensor. The zeroing mark detection unit 317 may include alight source (such as a halogen light), an optical imaging system, and acamera (such as a CCD camera), etc.

The zeroing mark detection unit 317 may irritate the zeroing mark on theencoder plate 306 using a wide band light from the light source, thecamera may receive the reflected signal from the zeroing mark using theoptical imaging system. Thus, the zeroing mark may be imaged on theviewing filed of the camera. After a signal processing of the image ofthe zeroing mark on the viewing field of the camera, a positionrelationship between the zeroing marks and the center of the viewingfield may be obtained.

The zeroing mark detection unit 317 may return the position relationshipinformation to the sub-control unit on the wafer stage 301, the waferstage 301 may be driven to adjust until the zeroing mark appear at thecenter of the viewing field. A coarse position information (informationobtained by the encoder plate readers 313) of the wafer stages 301 maybe obtained, and a coarse alignment of the wafer stage 301 may befinished.

A pull-in range of the camera of the zeroing mark detection unit 317 maybe approximately 100 μm˜300 μm. After the coarse alignment of the waferstage 301, a position accuracy of the wafer stage 301 may be in a rangeof approximately ±2 μm. The position accuracy may be sufficient forsubsequent wafer alignments and cylindrical reticle alignments.

Further, as shown in FIG. 4, the peripheral region 315 of the waferstage 301 may also have wafer stage fiducials 316. When the zeroing markdetection unit 317 is at a position of the zeroing detection mark, andthe coarse alignment is finished, the wafer stage 301 may move to causethe alignment detection unit 302 to detect the wafer stage fiducials 316of the wafer stage 301, a precise position information (informationdetected by the encoder plate readers 313) of the wafer stage 301 (orthe wafer stage fiducials 316) may be obtained. The precise positioninformation of the wafer stage 301 may be used as the zero position(origin) of the coordinate of the wafer stage 301, thus a fine alignmentof the wafer stage 301 may be achieved. In certain other embodiments,after the fine alignment of the wafer stage 301, the informationdetected by the encoder detector units 318 (as shown in FIG. 6) may becorrespondingly reset, the information after the resetting process maybe used as the zero position (origin) of the coordinate of the waferstage 301.

Since the wafer installed on the wafer stage 301 and the reticlealignment sensors 338 may be all on the surface of the wafer stage 301,the relative position of the wafer stage 301 and the wafer stagefiducials 316 may be fixed, and the relative position of the reticlealignment sensors 338 and the wafer stage fiducials 316 may also befixed, after the fine alignment of the wafer stage 301, the alignmentdetection units 302 (shown in FIG. 3) may detect the alignment marks onthe wafer, the position relationship between the alignment marks on thewafer and the wafer stage fiducials 316 may be obtained, and the wafermay be aligned. Further, the wafer stage 301 may move, alignment markson the cylindrical reticle 303 may be detected by a reticle alignmentdetection unit, the position relationship between the alignment marks onthe cylindrical reticle 303 and the wafer stage fiducials 316 may beobtained, thus the cylindrical reticle 303 may aligned. After aligningthe wafer and the cylindrical reticle 303, a position relationshipbetween the cylindrical reticle 303 and the wafer may be formed, thus aprecise exposure may be achieved on the exposure areas of the wafer.

When the alignment detection unit 302 detects the wafer stage fiducials316, an optical system of the alignment detection unit 302 may irradiatethe wafer stage fiducials 316, a reflected light from the wafer stagefiducials 316 may form an image on the viewing area of the camera of thealignment detection unit 302. After an imaging processing process of theimaging signal from the camera, the position relationship between thewafer stage fiducials 316 and the center of the viewing area of thecamera may be obtained. Then the position relationship information maybe sent back to the sub control units of the wafer stage 301. The subcontrol unit may drive the wafer stage 301 to adjust its position untilthe wafer stage fiducials 316 appears at the center of the viewing areaof the camera.

The wafer stage fiducials 316 may be formed by a plurality of gratingsdistributed along different directions. In one embodiment, the waferstage fiducials 316 are formed by first gratings along the x-directionand second gratings along the y-direction.

Further, referring to FIG. 3, the encoder plate 306 may fixed on thebase (not shown) of the exposure apparatus, a width of the encoder plate306 may be greater than a width of the wafer stage 301; and a length ofthe encoder plate 306 may be greater than a line distance between thealignment detection unit 302 and the optical exposure unit 309. Thus,when the wafer stage 301 is at the first position, the second position,and or moves from the first position to the second position, an accurateposition information may always be obtained by a position detection unitconsisting of the alignment detection unit 302 and the encoder plate306. The accurate position information may be obtained during analignment process and an exposure process, the exposure precision may beimproved. When the wafer stage 301 moves on other positions of the base,other appropriate methods may be used to detect the position, such asguide rails, photoelectrical sensors, or interferometers, etc.

As shown in FIG. 3, the encoder plate 306 may have the first opening 311(may refer as a metrology window) and the second opening 312 (may referas an exposure window). A position of the first opening 311 maycorrespond to a position of the alignment detection unit 302, i.e., thefirst opening 311 may be underneath the alignment detection unit 302.The first opening 311 may be used as an optical pass between thealignment detection unit 302 and the wafer stage 301. A position of thesecond opening 312 may correspond to a position of the opticalprojection unit 309, i.e., the second opening 312 may be underneath theoptical projection unit 309. The second opening may be used as anoptical pass between the optical projection unit 309 and the wafer stage301.

A detail structure of the encoder plate 306 is illustrated in FIG. 5. Asshown in FIG. 5, the encoder plate 306 may have a plurality of parallelequal groves 326 and heaves 325. The groves 326 and the heaves 325 mayform a reflective grating. The surface of the encoder plate 306 havingthe groves 326 and the heaves 325 may face the top surface of the waferstage 301. A distance between adjacent groves 326 and a distance betweenadjacent heaves 325 may be equal.

The encoder plate 306 may be made of glass, the groves 326 and theheaves 325 may be formed by etching the glass. In certain otherembodiments, opaque strips may be formed on the transparent glassencoder plate 306 to form the groves 326 and the heaves 325, that is thereflective grating. The opaque stripes may be made of any appropriatematerial, such as metal thin film, etc.

As shown in FIG. 5, in one embodiment, the encoder plate 306 may have afirst sub encoder plate 320 and a second sub encoder plate 321. Thefirst sub encoder plate 320 and the second sub encoder plate 321 may bedissymmetrical. A symmetrical center line AB of the first sub encoderplate 320 and the second sub encoder plate 321 and the connecting linebetween the alignment detection unit 302 and the center of the opticalprojection unit 309 may be on a same plane perpendicular to the base ofthe exposure apparatus. The symmetrical center line AB of the first subencoder plate 320 and the second sub encoder plate 321 and a connectingline between the center of the first opening 311 and the second opening312 may be coincide.

In one embodiment, the groves 326 and the heaves 325 of the first subencoder plate 320 and the groves 326 and the heaves 325 of the secondsub encoder plate 321 may be dissymmetrical. The heaves 325 (groves 326)of the first sub encoder plate 320 may connect with the symmetricalcenter line AB, and have a first angle 32. The heaves 325 (groves 326)of the second sub encoder plate 321 may connect with the symmetricalcenter line AB, and have a second angle 31. The angle of the secondangle 31 may be equal to the angle of the first angle 32. Thus, theaccuracy of the first sub encoder plate 320 may be identical to theaccuracy of the second sub encoder plate 321, a high accuracy of theposition coordinate of the wafer stage 301 detected by the encoder platereaders 313 may be obtained. A moving direction and displacement of thewafer stage 301 may be obtained by the phase change, interval change,and pulse number of signals detected by the encoder plate readers 313.

Angles of the first angle 32 and the second angle 31 may be in a rangeof approximately 5°˜85°. Specifically, the angle of the first angle 32and the second angle 31 may be 10°, 20°, 30°, 40°, 45°, 50°, 60°, 70°,or 80°, etc. When the wafer stage 301 moves under the first sub encoderplate 320 and the second sub encoder plate 321 along the x-axis, they-axis or the z-axis, phase and interval changes between two electricalsignals may be obtained by a single encoder detector unit 318. Incertain other embodiments, the phase and interval changes between aplurality signals may be obtained from a plurality of the encoderdetector units 318. The moving direction and displacement of the waferstage 301 may be determined and calculated by the obtainedphase/interval changes.

In one embodiment, the number of the encoder plate readers 313 may be atleast three; and each of the encoder plate readers 313 may include twoencoder detector units 318. The encoder plate readers 313, the first subencoder plate 320 and the second sub encoder plate 321 may form adetection system. Each of the encoder plate readers 313 may detect twodegrees of freedom of the wafer stage 301, including the x-direction (orthe y-direction) and the z-direction. A detection of six degrees offreedom may be achieved using at least three encoder plate readers 313.The six degrees of freedom may include the x-direction, the y-direction,the z-direction, the rotation x-direction, the rotation y-direction, andthe rotation z-direction. The detection of these directions may besimple with a high accuracy, and the data processing may also be simple.

FIG. 6 illustrates an exemplary embodiment using a detection systemconsisting of four encoder plate readers 313, the first sub encoderplate 320 and the second sub encoder plate 321 to detect a position ofthe wafer stage 301. As shown in FIG. 6, the four encoder plate readers313 may include a first encoder plate reader 313 a, a second encoderplate reader 313 b, a third encoder plate reader 313 c, and a fourthencoder plate reader 313 d. Distances between the center of the surfaceof the wafer stage 301 and the first encoder plate reader 313 a, thesecond encoder plate reader 313 b, the third encoder plate reader 313 c,and the fourth encoder plate reader 313 d may be equal. The distance mayrefer as a “r”. Connecting lines of the centers of the four encoderplate readers may form a rectangle.

The x-axis coordinate of the wafer stage 301 obtained by the detectionsystem may refer as a C_(x). The y-axis coordinate of the wafer stage301 obtained by the detection system may refer as a C_(y). The z-axiscoordinate of the wafer stage 301 obtained by the detection system mayrefer as a C_(z). The x-axis rotation constant obtained by the detectionsystem may refer as a R_(x). The y-axis rotation constant obtained bythe detection system may refer as a R_(y). The z-axis rotation constantobtained by the detection system may refer as a R_(z). Wherein:

$;{{Cx} = \frac{E_{2} + E_{3} - E_{1} - E_{4}}{2\sqrt{2}}};$${{Cy} = {- \frac{E_{1} + E_{2} + E_{3} + E_{4}}{2\sqrt{2}}}};$${Cz} = \frac{E_{1\; z} + E_{2\; z} + E_{3\; z} + E_{4\; z}}{4}$${{Rx} = \frac{E_{1\; z} + E_{2\; z} - E_{3\; z} - E_{4\; z}}{4\; S_{y}}};$${{Ry} = \frac{E_{2\; z} + E_{3\; z} - E_{1\; z} - E_{4\; z}}{4\; S_{x}}};$${Rz} = {- \frac{E_{4} - E_{3}}{2\; r}}$

The above equations may be correct when the 2 encoder plates are angledat 45 degrees to the symmetry axis and orthogonal to each other.Wherein: E₁, E₂, E₃, and E₄ may refer to detected values obtained by thefirst encoder plate reader 313 a, the second encoder plate reader 313 b,the third encoder plate reader 313 c, and the fourth encoder platereader 313 d when the wafer stage 301 moves along the x-direction and/orthe y-direction, respectively. E_(1z), E_(2z), E_(3z), and E_(4z) mayrefer to detected values obtained by the first encoder plate reader 313a, the second encoder plate reader 313 b, the third encoder plate reader313 c, and the fourth encoder plate reader 313 d when the wafer stage301 moves along the z-direction, respectively. S_(y) may refer to avertical distance between the connecting line of the centers of thefirst encoder plate reader 313 a and the second encoder plate reader 313b and the center of the surface of the wafer stage 301. S_(x) may referto a vertical distance between the connecting line of the centers of thefirst encoder plate reader 313 a and the second encoder plate reader 313d and the center of the surface of the wafer stage 301.

Referring to FIG. 5, when the encoder plate 306 and the encoder detectorunits 318 are used to form a position detection unit, a detectionaccuracy the position detection unit may be in a range of approximately1 nm˜10 nm. When the wafer stage 301 moves within the regime of theencoder plate 306, the position error of the wafer stage 301 may besmaller than a range of approximately 1 nm˜10 nm. A precise positionrelationship between the wafer stage 301, the wafer on the wafer stage301, and the cylindrical reticle 303 may be achieved, thus the exposureapparatus may have a relatively high accuracy.

Further, as shown in FIG. 5, the encoder plate 306 in the peripheralregion of the first opening 311 may have zeroing marks 322. The zeroingmarks 322 may be used for a quick alignment and leveling capture. Anumber of the zeroing marks 322 may be equal to the number of thezeroing mark detection units 317. A distribution of the zeroing marks322 may be same as a distribution of the zeroing mark detection units317 on the wafer stage 301. That is, a pattern formed by centerconnecting lines of the zeroing marks 322 on the encoder plate 306 maycoincide with a pattern formed by center connecting lines of the zeroingdetection units 317 on the wafer stage 301. Thus, an accuratepositioning of the wafer stage 301 may be achieved.

In one embodiment, the number of the zeroing marks 322 is correspondingto the number of the zeroing mark detection units 317. The number of thezeroing marks 322 may be four. As shown in FIG. 5, each of the zeroingmarks 322 may have a plurality of first grating 323 distributed alongthe y-axis direction and a plurality of the second grating 324distributed along the y-axis direction.

Further, referring to FIG. 3, the reticle stage 305 may include areticle stage frame (not shown) and a center shaft extension tube (notshown) fixed at one side of the reticle stage frame. The first bearing304 a may be fixed on one end of the center shaft extension tube nearthe reticle stage frame. The second bearing 304 b may be fixed on theother end of the center shaft extension tube. In certain otherembodiment, the second bearing 304 b may be a removable bearing, i.e.,may be installed on installed on the center shaft extension tube bycertain control units. Two side faces of the first bearing 304 a and thesecond bearing 304 facing each other may have slots. The cylindricalreticle 303 may be clamped in the slots of the side faces of the firstbearing 304 a and the second bearing 304 b. When the first bearing 304 aand the second bearing 304 b rotate around the center shaft extensiontube, the cylindrical reticle 303 may also rotate around the centershaft extension tube. Wherein, the center axis of the center shaftextension tube may be equivalent to the center axis of the cylindricalreticle 303. Certain drive units may be connected with the first bearing304 a and the second bearing 304 b to drive them to rotate around thecenter shaft extension tube.

The cylindrical reticle 303 may be a hollow cylinder. Designed patternsmay be formed on the inner surface and/or outer surface of thecylindrical reticle 303

Referring to FIG. 3, the center shaft extension tube may have anillumination slit (not shown) penetrating through the bottom, and theilluminator box 308 may be installed in the center shaft extension tube.Light illuminating from the illuminator box 308 may reach on thecylindrical reticle 303 through the illumination slit. Then lightilluminating through the reticle 303 may be projected on the exposureareas of the wafer on the wafer stage 301 by the optical projection unit309, and the wafer may be exposed.

Various light sources may be used as the illumination box 308. In oneembodiment, the illumination box 308 may be a KrF excimer laser(wavelength may be approximately 248 nm) or an ArF excimer laser(wavelength may be approximately 193 nm). The illumination box 308 mayalso be an F₂ laser (wavelength may be approximately 157 nm), or anultraviolet light source (wavelength is approximately 13.5 nm), etc. Thelight of the illumination box 308 may also be a glow discharge in theultraviolet region generated from a high pressure mercury light source(i line, or g line, etc).

A projected length of the perimeter of the outer surface of thecylindrical reticle 303 projected by the optical projection unit 309 maybe equal to a length of an exposure area on a wafer (along a scanningdirection). That is, referring to FIG. 3, when the cylindrical reticle303 rotates around the center shaft extension tube 329 for one cycle, atthe same time, the wafer stage 301 scans one exposure region along thescanning direction (the arrow direction shown in FIG. 3), patterns onthe cylindrical reticle 303 may be completely transferred to an exposureregion on the wafer. The cylindrical reticle 303 may continue rotating,and the wafer stage 301 keeps scanning along the scanning direction, thepatterns on the cylindrical reticle 303 may be completely transferred toa next exposure region on the wafer.

The rotating and scanning process may be repeated, a column of exposureareas distributed along the scanning direction may be all exposed.During the exposure process of the exposure areas, it may be unnecessaryfor the cylindrical reticle 303 to change the rotation direction, and itmay be unnecessary for the wafer stages to change the scanning directionas well. Thus, when the exposure area is changed, it may be unnecessaryto have an accelerating process or a decelerating process. When a seriesof exposure areas along the scanning direction are exposed continuously,the wafer stages may keep a constant scanning speed. Therefore, the timefor exposure processes may be significantly reduced, and the exposureefficiency of the exposure apparatus may be increased.

In certain other embodiments, the projected length of the perimeter ofthe outer surface of the cylindrical reticle 303 projected by theoptical projection unit 309 may be equal to a length of a plurality ofexposure regions on a wafer (along a scanning direction). That is, whenthe cylindrical reticle 303 rotates around the center shaft extensiontube for one cycle, the wafer stage 301 scans on the plurality ofexposure regions (an entire column of exposure regions) along thescanning direction at the same time. A plurality of exposure regions maybe exposed at same time. The exposure efficiency may be furtherincreased.

The cylindrical reticle 303 may have a plurality of the reticlealignment marks (not shown). The peripheral region 315 of the waferstage 301 may have a plurality of reticle detection units. The reticledetection units may be used to detect the reticle alignment marks, aposition relationship between the reticle alignment 303 and the waferstage 301 may be formed, thus the cylindrical reticle 303 may bealigned.

The optical projection unit 309 may be used to project the light passingthrough the cylindrical reticle 303 on the exposure areas of the waferon the wafer stage 301. When a KrF excimer laser or an ArF excimer laseris used as the light source in the illuminator box 308, the opticalprojection unit 309 may be a refraction system, only made of opticalrefraction devices (such as lenses). When an F₂ laser is used as thelight source in the illuminator box 308, the optical projection unit 309may be a deflection/refraction system, made of optical refractiondevices, optical reflection devices, or a combination thereof.

FIGS. 7-14 illustrate certain steps of an exemplary exposure processusing the above disclosed exposure apparatus. For illustrative purposes,an exposure apparatus with four wafer stages may be used to describe theexposure process in details.

As shown in FIG. 7, the exposure apparatus has four wafer stagesincluding a first wafer stage 3011, a second wafer stage 3012, a thirdwafer stage 3013, and a fourth wafer stage 3014. A first wafer 1, asecond wafer 2, a third wafer 3 and a fourth wafer 4 may be successivelyloaded on the first wafer stage 3011, the second wafer stage 3012, thethird wafer stage 3013, and the fourth wafer stage 3014.

Before the exposure apparatus starts working, the first wafer stage3011, the second wafer stage 3012, the third wafer stage 3013, and thefourth wafer stage 3014 may distribute in queue on the base of theexposure apparatus. When the exposure process is started, exposureprograms may be firstly installed in the exposure apparatus. Then fourwafers may be loaded on the four wafer stages successively. The waferstages loaded with wafers may successively move toward a first positionto align the wafers at the first position.

When the first wafer stage 3011, the second wafer stage 3012, the thirdwafer stage 3013, and the fourth wafer stage 3014 move in regionsoutside the encoder plate 306, tracks, interferometers, or gratingplates may be used to detect their positions. The accumulated positionerrors may be less than 100 μm.

Further, as shown in FIG. 8, the first wafer stage 3011 moves to thefirst position of the base, i.e., a pre-alignment position underneaththe first opening 311 of the encoder plate 306, the zeroing markdetection units 317 (shown in FIG. 5) on the first wafer stage 3011 maydetect the zeroing marks 322 on the encoder plate 306, a coarse positioninformation of the first wafer stage 3011 may be obtained, and a coarsealignment of the first wafer stage 3011 may be finished.

In one embodiment, if at least three zeroing mark detection units 317have detected the corresponding zeroing marks 322, the coarse alignmentof the wafer stage 3011 may be finished. If less than three zero markdetection units 317 have detected the corresponding zeroing marks 322,the coarse alignment may need to repeat.

After the coarse alignment of the wafer stage 3011 is finished, thewafer stage 3011 may quickly to move under the alignment detection unit302 (referring to FIG. 3), the alignment detection unit 302 may detectthe wafer stage fiducials 316 on the first wafer stage 3011, an accurateposition information of the wafer stage 3011 (or wafer stage fiducials316) may be obtained. At the same time, the accurate positioninformation of the wafer stage 3011 may be used as a zero point (origin)of a position coordinate of the wafer stage 3011, and a fine alignmentof the wafer stage 3011 may be finished.

In certain other embodiments, after finishing the fine alignment of thewafer stage 3011, the detected information of the encoder plate readers313 on the wafer stage 3011 may be reset correspondingly, the reset zeroinformation may be used as the zero (origin) of the position coordinateof the wafer stage 3011. The main control unit 300 may save andcalculate the displacement bias of the wafer stage 3011 between the finealignment and the coarse alignment.

After the alignment detection units 302 detect the wafer stage fiducials316 on the first wafer stage 3011, the first wafer stage 3011 may move,the alignment detection unit 302 may detect alignment marks on the firstwafer 1 loaded on the first wafer stage 3011, the position informationof the alignment marks on the first wafer 1 may be obtained. The maincontrol unit 300 may convert the position information of the alignmentmarks on the first wafer 1 to a position coordinate using the positioninformation of the wafer stage fiducials 316 as an origin, a positionmanagement of exposure regions on the wafer 1 may be achieved. Therelated position information and position coordinate may be saved in themain control unit 300, and an alignment of the first wafer 1 may befinished. The main control unit 300 may save and calculate thedisplacement bias of the wafer stage 3011 between the fine alignment andthe detection of the alignment marks on the first wafer 1.

As shown in FIG. 9, after the alignment of the wafer 1, the first waferstage 3011 may move from the first position to the second position,i.e., a pre-exposure position underneath the second opening 312 of theencoder plate 306. Then, the wafer stage 3011 may perform aunidirectional scan along a scanning direction, i.e., the positivedirection of the y-axis. At the same time, the cylindrical reticle 303may rotate around the center axis of the cylindrical reticle stage 305.Light passing through the cylindrical reticle 303 may be projected onthe first wafer 1 on the first wafer stage 3011 by the opticalprojection unit 309 (shown in FIG. 3), thus a first column of exposureregions along the scanning direction may be exposed. At the same time,the second wafer stage 3012 may move to the first position of the base,and the second wafer 2 on the second wafer stage 3012 may be aligned.

Before exposing the first wafer 1, the reticle alignment detection uniton the first wafer stage 3011 may detect the reticle alignment marks onthe cylindrical reticle 303, a position information of the reticlealignment marks may be obtained. Thus, a position relationship betweenthe cylindrical reticle 303 and the first wafer 1 may be formed as well,and an alignment of the cylindrical reticle 303 may be finished. Therelated position information and position coordinate may be saved in themain control unit 300.

When the first column of exposure regions of the first wafer 1 areexposed, the wafer stage 3011 may keep the positive scanning directionof the y-axis, the rotation direction of the cylindrical reticle 303around the center axis of the cylindrical reticle stage 305 may alsokeep same, thus after exposing the first exposure region of the firstcolumn of exposure regions, it may unnecessarily change the scanningdirection of the first wafer stage 3011 and the rotation direction ofthe cylindrical reticle 303, a second exposure region of the firstcolumn of exposure regions may be exposed. Similarly, all the exposureregions of the first column may be exposed without changing the scanningdirection of the first wafer stage 3011 and the rotation direction ofthe cylindrical reticle 303. Thus, when the first column of exposureregions of the first wafer 1 are exposed, it may be unnecessary for thefirst wafer stage 3011 to accelerate or decelerate, the time for theexposure process may be significantly reduced.

Before exposing the first exposure region of the first column ofexposure regions of the first wafer 1, the first wafer stage 3011 mayneed an acceleration process. After exposing the last exposure region ofthe first column of exposure region, the first wafer stage 3011 may needa deceleration process.

In one embodiment, since the scanning direction of the first wafer stage3011 may keep constant, on the basis providing a relatively highexposure resolution, the scanning speed may be increased. The scanningspeed of the first wafer stage 3011 may be in a range of approximately100 mm/s˜10 m/s, or higher. Physically, the scanning speed may have nolimitation except the position detections and the feedback time.

The time for the cylindrical reticle 303 to rotate around the centeraxis of the cylindrical reticle stage 305 for one circle may be equal tothe time for the first wafer stage 3011 to move one exposure regionalong the scanning direction. Thus, patterns of the cylindrical reticle303 may be completely transferred onto the exposure regions on the firstwafer 1, and an unidirectional step scanning exposure of the exposureregions on the first wafer 1 may be achieved.

In certain other embodiments, the time for the cylindrical reticle 303to rotate around the center axis of the cylindrical reticle stage 305for one circle may be equal to the total time for the first wafer stage3011 to move a plurality of exposure regions along the scanningdirection. When the cylindrical reticle 303 rotates for one circle, aplurality of exposure regions of the first column of exposure regionsalong the scanning direction may be exposed.

When the first column of exposure regions of the first wafer 1 on thefirst wafer stage 3011 are partially exposed, after finishing thealignment the second wafer 2, the second wafer stage 3012 may move fromthe first position toward the second position, or a nearby position onthe base to wait for an exposure. The third wafer stage 3013 may move tothe first position to align the third wafer 3. Then, the fourth waferstage 3014 may move toward the first position after loading the fourthwafer 4. The alignment of the second wafer 2 is similar as the alignmentof the first wafer 1.

As shown in FIG. 10, when the exposure of the first column of exposureregions of the first wafer 1 on the first wafer stage 3011 is completed,the first wafer stage 3011 may continue to move along the positivedirection of the y-axis, the second wafer stage 3012 may move to thesecond position. Then, the second wafer stage 3012 may perform anunidirectional scan along the scanning direction, i.e., the positivedirection of the y-axis. At the same time, the cylindrical reticle 303may rotate around the center axis of the cylindrical reticle stage 305,the light passing through the cylindrical reticle 303 may be projectedon the second wafer 2 loaded on the second wafer stage 3012 by theoptical projection unit 309. A first column of exposure regions of thesecond wafer 2 along the scanning direction may be exposed. At the sametime, after aligning the third wafer 3, the third wafer stage 3013 maymove from the first position toward the second position. The fourthwafer stage 3014 move to the first position, and the fourth wafer 4 maybe aligned.

Before exposing the second wafer 2, the reticle alignment detection uniton the first wafer stage 3012 may detect the reticle alignment marks onthe cylindrical reticle 303, a position information of the reticlealignment marks may be obtained, and a position relationship between thecylindrical reticle 303 and the second wafer stage 3012 may be formed.Thus, a position relationship between the cylindrical reticle 303 andthe second wafer 2 may be formed, and an alignment of the cylindricalreticle 303 may be finished. The related position information andposition coordinate may be saved in the main control unit 300.

As shown in FIG. 11, the first wafer stage 3011 may move toward thefirst position. After the first column of exposure regions of the secondwafer 2 are exposed along the scanning direction, the second wafer stage3012 may move away from the second position, and the third wafer stage3013 may move to the second position. Then, the third wafer stage 3013may perform a unidirectional scan along the scanning direction, i.e.,the positive direction of the y-axis. At the same time, the cylindricalreticle 303 may rotate around the center axis of the cylindrical reticlestage 305, and the light passing through the cylindrical reticle 303 maybe projected on the third wafer 3 loaded on the third wafer stage 3013by the optical projection unit 309. A first column of exposure regionsof the third wafer 3 along the scanning direction may be exposed. At thesame time, after aligning the fourth wafer 4, the fourth wafer stage3014 may move from the first position toward the second position.

Before exposing the third wafer 3, the reticle alignment detection uniton the first wafer stage 3013 may detect the reticle alignment marks onthe cylindrical reticle 303, a position information of the reticlealignment marks may be obtained, and a position relationship between thecylindrical reticle 303 and the third wafer stage 3013 may be formed.Thus, a position relationship between the cylindrical reticle 303 andthe third wafer 3 may be formed, and an alignment of the cylindricalreticle 303 may be finished. The related position information andposition coordinate may be saved in the main control unit 300.

As shown in FIG. 12, after the first column of exposure regions of thethird wafer 3 are exposed, the first wafer stage 3011 may move to thefirst position. The first wafer 1 on the first wafer stage 3011 may bealigned. The fourth wafer stage 3014 may move to the second position.Then, the fourth wafer stage 3014 may perform a unidirectional scanalong the scanning direction, i.e., the positive direction of they-axis. At the same time, the cylindrical reticle 303 may rotate aroundthe center axis of the cylindrical reticle stage 305, and the lightpassing through the cylindrical reticle 303 may be projected on thefourth wafer 4 loaded on the fourth wafer stage 3014 by the opticalprojection unit 309. A first column of exposure regions of the fourthwafer 4 along the scanning direction may be exposed.

Since the main control unit 300 may be used to save and calculate thedisplacement bias of the wafer stage 3011 between the fine alignment andthe coarse alignment and the displacement bias of the wafer stage 3011between the fine alignment and the detection of the alignment marks onthe first wafer 1, when the first wafer 1 on the first wafer stage 3011is realigned, it may only need the zeroing mark detection unit 317 todetect the zeroing marks 322 on the encoder plate 306, the positioncoordinate of the wafer stage 3011 may be obtained by the main controlunit 300 using the coarse position information of the first wafer stage3011 and certain types of calculation. Thus, a position management ofthe first wafer 1 may be achieved, and the time for a realignment of thefirst wafer 1 may be reduced.

In certain other embodiments, when the first wafer 1 is realigned, thealignment detection unit 302 may detect the wafer stage fiducials on thefirst wafer stage 1 and the alignment marks on the first wafer 1.

Further, as shown in FIG. 13, the first wafer stage 3011 may move fromthe first position to the second position, then the first wafer stage3011 may perform a unidirectional scan along the scanning direction,i.e., the positive direction of the y-axis. At the same time, thecylindrical reticle 303 may rotate around the center axis of thecylindrical reticle stage 305, and the light passing through thecylindrical reticle 303 may be projected on the first wafer 1 on thefirst wafer stage 3011 by the optical projection unit 309. A secondcolumn of exposure regions of the first wafer 1 along the scanningdirection may be exposed. At the same time, the second wafer stage 3012may move to the second position of the base, the second wafer 2 on thesecond wafer stage 3012 may be aligned.

In one embodiment, since the position relationship between thecylindrical reticle 303 and the first wafer stage 3011 may be alreadyformed when the first column of exposure regions of the first wafer 1are exposed, it may unnecessarily detect the reticle alignment marks, aposition relationship between the cylindrical reticle 303 and the firstwafer stage 3011 for exposing the second column of exposure regions maybe obtained by the main control unit 300 using the saved positionrelationship between the cylindrical reticle 303 and the first waferstage 3011, and the displacement of the first wafer stage 3011 movingalong the x direction, i.e., a distance along the x-direction for thewafer stage 3011 to move one exposure region comparing with the firstcolumn of exposed regions after aligning the first wafer 1 and beforeexposing the second column of exposure regions, the exposure time may beeffectively reduced.

In certain other embodiments, before exposing the second column ofexposure regions of the first wafer 1, the reticle alignment detectionunit may detect the reticle alignment marks on the cylindrical reticle303, the position relationship between the cylindrical reticle 303 andthe first wafer stage 3011 may be obtained.

Further, as shown in FIG. 14, after the second column of exposureregions of the first wafer 1 are exposed, the first wafer stage 3011 maycontinue to move toward the first position of the base along thepositive direction of the y-axis, and the second wafer stage 3012 maymove to the second position. Then the second wafer stage 3012 mayperform an unidirectional scan along the scanning direction, i.e., thepositive direction of the y-axis. At the same time, the cylindricalreticle 303 may rotate around the center axis of the cylindrical reticlestage 305, and the light passing through the cylindrical reticle 303 maybe projected on the second wafer 2 on the second wafer stage 3012 by theoptical projection unit 309. A second column of exposure regions of thesecond wafer 2 along the scanning direction may be exposed. At the sametime, after the third wafer 3 is aligned, the third wafer stage 3013 maymove from the first position toward the second position of the base. Thefourth wafer stage 3014 may move to the first position 311, and thefourth wafer 4 on the fourth wafer stage 3014 may be aligned.

The first wafer stage 3011, the second wafer stage 3012, the third waferstage 3013, and the fourth wafer stage 3014 may cyclically move on thebase in a pipelined mode. The alignment and exposure processes may berepeated until all the exposure regions of the first wafer 1, the secondwafer 2, the third wafer 3 and the fourth wafer 4 are exposed. When acertain wafer on one of the four wafer stages are completely exposed, anew wafer may be loaded.

The present exposure apparatus may have the cylindrical reticle 303 anda plurality of wafer stages 301. The cylindrical reticle 303 may rotatearound the center axis of the cylindrical reticle stage 305, one waferstage 301 may perform an unidirectional scan along the scanningdirection, the light passing through the cylindrical reticle 303 may beprojected on a certain column of exposure regions on the wafers on thewafer stage 301, thus the certain column of exposure regions may beexposed along the scanning direction. When the certain column ofexposure regions are exposed, since the cylindrical reticle 303 mayreturn to the origin after rotating one circle, after exposing thecertain column of the exposed areas, it may unnecessarily change therotation direction of the reticle 303 and the scanning direction of thewafer stage 301 an exposure of a next exposure region in the same columnmay be achieved. Therefore, it may unnecessarily need an acceleratingprocess and a decelerating process when exposure regions in a samecolumn are exposed, the total time for an exposure process maysignificantly reduced, and the yield in per unit time of the exposureapparatus may be increased.

In one embodiment, using the cylindrical reticle 303 may have a similarreticle alignment process as other exposure apparatuses. However thewafer exposure map may be changed. Each column of exposure regions isunidirectional scan-exposed during one scan instead of one exposureshot. The only time loss may be to scan back the wafer for next columnexposure. The throughput gain may be still substantial: For example: fora two-wafer stage configuration (alignment and leveling may be done inparallel, and may unnecessarily be counted as a throughput overhead),currently, each exposure area may need 0.26 seconds for entire scan,including acceleration (0.10 sec), scan-exposure (0.06 sec),de-acceleration (0.10 sec). For a scan speed of 600 mm/s and 300 mmwafer, each column may only need about 2 times (back scan to prepare fornext column exposure) of (0.1 sec+0.5+0.1 sec), but it may include theexposure of up to 9 shots (average of 7 shots), the time gain is:0.26×7−0.7×2=1.82−1.4=0.42 sec, or 30% throughput gain. If the scanspeed may be further increased, for example, 2 msec, assuming theacceleration and de-acceleration may use the same time, the gain will bemore: 0.22×7−0.36×2=1.54−0.72=0.82 sec, i.e., a 114% yield gain.

For a plurality of wafer stages, the gain in yield may be more sincewhen one exposed wafer is going back to the first position, other wafersmay be exposed. For example, in case of a 25 wafer stage systems, if onewafer has 12 columns of exposure regions, the total processing time for25 wafers may be estimated as: [(0.1+0.54+0.1+0.06×2 (time lag betweenwafer stage to wafer stage))×12 (column)+2 (first column reticlealignment)]×25=308 seconds, i.e., the yield will be 3600/308×25=292 wphwhich may be significantly higher than the yield of current methods,which may be about 3600/[(0.1+0.06+0.1)×110]=126 wph. Wherein, “wph” mayrefer to wafer per hour.

In certain other embodiments, the exposure system may have one waferstage 301, the wafer stage 301 may unnecessarily go back the firstposition after the first column of the wafer is exposed. The wafer stage301 may only need move to a next exposure region, and perform anunidirectional scan. At the same time, the cylindrical reticle 303 mayrotate for one cycle, the next exposure region may be exposed. Theexposure process may be repeated until the entire wafer is exposed.

The above detailed descriptions only illustrate certain exemplaryembodiments of the present invention, and are not intended to limit thescope of the present invention. Those skilled in the art can understandthe specification as whole and technical features in the variousembodiments can be combined into other embodiments understandable tothose persons of ordinary skill in the art. Any equivalent ormodification thereof, without departing from the spirit and principle ofthe present invention, falls within the true scope of the presentinvention.

What is claimed is:
 1. An exposure apparatus, comprising: a base; awafer stage group having a plurality of wafer stages on the base forholding wafers and successively moving from a first position to a secondposition of the base cyclically; an alignment detection unit above thefirst position for detecting wafer stage fiducials on the wafer stage atthe first position and alignment marks on a wafer on the wafer stage atthe first position to align the wafer; a reticle stage on the secondposition for loading a cylindrical reticle and causing the cylindricalreticle to rotate around a center axis of the reticle stage; and anoptical projection unit between the reticle stage and the base forprojecting light passing through the cylindrical reticle on exposureregions of a wafer on the wafer stage, wherein a control system isconfigured to control the wafer stage group such that: when the waferstage moves from the first position to the second position, the waferstage performs a unidirectional scan along an scanning direction, thecylindrical reticle rotates around the center axis of the reticle stage,the light passing through the cylindrical reticle is projected onto thewafer on the wafer stage, and a column of exposure regions on the waferalong the scanning direction are exposed, and a first column of exposureregions on a first wafer and a corresponding column of exposure regionson a second wafer are each exposed prior to exposing a second column ofthe exposure regions on the first wafer.
 2. The exposure apparatusaccording to claim 1, wherein: the wafer stages are driven by a magneticsuspension system.
 3. The exposure apparatus according to claim 2,wherein: each of the wafer stages has a corresponding sub control unitfor controlling positioning, moving and alignment of the wafer stage,and for communicating with the magnetic suspension system and thealignment detection unit.
 4. The exposure apparatus according to claim3, further including: a main control unit communicating with the waferstage, the alignment detection unit, the optical projection unit, andthe sub control unit, and managing alignment and exposure of the wafer.5. The exposure apparatus according to claim 4, wherein: the sub controlunit of the wafer stage communicates with the main control unit by awireless communication technology.
 6. The exposure apparatus accordingto claim 5, wherein: each of the wafer stages has a power storage unitstoring power for operating the wafer stage.
 7. The exposure apparatusaccording to claim 6, wherein the exposure apparatus further includes: acable connection unit for forming a detachable connection between acharging cable and the power storage unit for charging the power storageunit when the charging cable and the power storage unit are connected.8. The exposure apparatus according to claim 7, wherein: a fixed ordetachable connection is used between the charging cable and the waferstage when the number of the wafer stage is two; and the detachableconnection is used between the charging cable and the wafer stage when anumber of the wafer stages is greater than two.
 9. The exposureapparatus according to claim 1, further including: a position detectionsystem for detecting the position information of the wafer stage,wherein: the position detection system includes the alignment detectionunit, an encoder plate between the optical projection unit and the waferstage, and encoder plate readers on the top surface of the wafer stage.10. The exposure apparatus according to claim 9, wherein: the encoderplate has a plurality of groves and heaves; a reflection grating isformed by the groves and the heaves with an alternative distribution;and a surface of the encoder plate having the groves and the heavesfaces the top surface of the wafer stage.
 11. The exposure apparatusaccording claim 9, wherein: the encoder plate includes a first subencoder plate and a second sub encoder plate; the first sub encoderplate and the second sub encoder plate are dissymmetrical; and asymmetrical line between the first sub encoder plate and the second subencoder plate and a connecting line between the alignment detection unitand the center of the optical projection unit are in a same planeperpendicular to the base.
 12. The exposure apparatus according to claim9, wherein: a width of the encoder plate is greater than a width of thewafer stage; a length of the encoder plate is greater than a linedistance between the alignment detection unit and the center of theoptical projection unit; the encoder plate has a first opening and asecond opening; the first opening is at a position corresponding to thealignment detection unit; and the second opening is at a positioncorresponding to the optical projection unit.
 13. The exposure apparatusaccording to claim 9, wherein: a surface of the wafer stage has a waferholding region and a peripheral region surrounding the wafer holdingregion; the encoder plate readers are in the peripheral region of thetop surface of the wafer stage; each of the encoder plate readers hastwo encoder plate readers; and each of the encoder plate readers has anoptical emission unit for emitting light, an optical receiver unit forreceiving reflected light from the encoder plate and converting thereflected light to electrical signals, and a recognition unit forobtaining the displacement of the wafer stage by orienting and countingthe electrical signals.
 14. The exposure apparatus according to claim13, wherein: a number of the encoder plate readers is at least threelocating at different positions of the peripheral region of the waferstage.
 15. The exposure apparatus according to claim 13, wherein: theencoder plate at a surrounding region of a first opening has zeroingmarks; each of the encoder plate readers has zeroing mark detectionunits for detecting the zeroing marks; a number of the zeroing marks isequal to a number of the zeroing mark detection units; and adistribution of the zeroing marks on the encode plate is same as adistribution of the zeroing mark detection units.
 16. The exposureapparatus according to claim 1, wherein: the cylindrical reticle is ahollow cylinder; the surface of the cylindrical reticle has patterns;and a projected length of the perimeter of the outer surface of thecylindrical reticle projected by the optical projection unit is equal toa length of an exposure area on a wafer, or a total length of aplurality of the exposure regions.
 17. The exposure apparatus accordingto claim 16, wherein: the cylindrical reticle has reticle alignmentmarks; the wafer stage has reticle alignment sensors; and the reticlealignment sensors are used to detect the reticle alignment marks toalign the cylindrical reticle.
 18. An exposure method, comprising: Step1, installing wafers successively on a plurality of wafer stages; Step2, moving the wafer stages holding the wafers to a first positionsuccessively, detecting stage fiducials on the wafer stages andalignment marks on the wafers to align the wafers; Step 3, moving thewafer stage having the aligned wafer from the first position to a secondposition and performing an unidirectional scanning along a scanningdirection; rotating a cylindrical reticle around a center axis of areticle stage; projecting light passing through the cylindrical reticleonto the wafers on the wafer stages; and exposing a first column ofexposure regions on a first wafer and a corresponding column of exposureregions on a second wafer along the scanning direction; Step 4, movingthe wafer stage holding the partially exposed wafer from the secondposition to the first position after exposing the first column of theexposure regions on a first wafer and the corresponding column of theexposure regions on the second wafer; and Step 5, repeating the Step 2to the Step 4 including exposing a second column on the first wafer,until a predetermined number of columns of exposure regions on eachwafer on the wafer stage are exposed.
 19. The exposure method accordingto claim 18, before detecting the stage fiducials, further including:detecting zeroing marks on an encoder plate using the zeroing markdetection units to obtain fiducial position information of the waferstage.
 20. The exposure method according to claim 18, wherein: a timelength for the cylindrical reticle to rotate around the center axis ofthe reticle stage for one cycle is equal to a time length for the waferstage to move one exposure region along the scanning direction.